When Python is installed, a number of configuration options are stored in the Windows registry. The Windows registry provides a central location where programs can store their preferences and settings and provides more features than traditional techniques of saving configuration information. The Windows registry also has some limitations, and many people would dearly like to see it suffer a slow and painful death! Whatever your views, good Windows applications, and therefore Python, store their information in the Windows registry.
In general, it isn’t necessary for you to understand or edit the registry; Python and any extensions you install normally manages this for you. Indeed, if you are unfamiliar with the Windows registry, you should avoid it completely: it’s all too easy to do serious damage to your PC’s configuration. However, if you are experienced with the Windows registry or are curious to see how everything works, read on.
The most important configuration option stored in the registry is the PythonPath, the list of directories where Python looks to find modules, which can be viewed at runtime via sys.path . Under Unix, the common way of storing this option is by setting a PYTHONPATH environment variable. Under Windows, this information is stored in the registry rather than in the environment.
Python also stores other configuration data in the registry, including the location where Python was installed, a list of Python help files, and so forth. ...